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Biologically fixed N2 as a source for the N2O production in a grass clover mixture, measured by 15N2

Carter, Mette S. and Ambus, Per (2006) Biologically fixed N2 as a source for the N2O production in a grass clover mixture, measured by 15N2. Nutrient Cycling in Agroecosystems, 74, pp. 13-26.

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Summary

The contribution of biologically fixed dinitrogen (N2) to the nitrous oxide (N2O) production in grasslands is unknown. To assess the contribution of recently fixed N2 as a source of N2O and the transfer of fixed N from clover to companion grass, mixtures of white clover and perennial ryegrass were incubated for 14 days in a growth cabinet with a 15N2-enriched atmosphere (0.4 atom% excess). Immediately after labelling, half of the grass-clover pots were sampled for N2 fixation determination, whereas the remaining half were examined for emission of 15N labelled N2O for another eight days using a static chamber method. Biological N2 fixation measured in grass-clover shoots and roots as well as in soil constituted 342, 38 and 67 mg N m-2 d-1 at 16, 26 and 36 weeks after emergence, respectively. The drop in N2 fixation was most likely due to a severe aphid attack on the clover component. Transfer of recently fixed N from clover to companion grass was detected at 26 and 36 weeks after emergence and amounted to 0.7 ± 0.1 mg N m-2 d-1, which represented 1.7 ± 0.3 % of the N accumulated in grass shoots during the labelling period. Total N2O emission was 91, 416 and 259 μg N2O-N m-2 d-1 at 16, 26 and 36 weeks after emergence, respectively. Only 3.2 ± 0.5 ppm of the recently fixed N2 was emitted as N2O on a daily basis, which accounted for 2.1 ± 0.5 % of the total N2O-N emission. Thus, recently fixed N released via easily degradable clover residues appears to be a minor source of N2O.


EPrint Type:Journal paper
Keywords:emission factor, nitrogen fixation, nitrogen transfer, nitrous oxide, 15N2, white clover
Subjects: Crop husbandry > Production systems > Pasture and forage crops
Environmental aspects > Air and water emissions
Research affiliation: Denmark > DARCOF II (2000-2005) > I.13 (DINOG) Dinitrogen fixation and nitrous oxide losses in grass-clover pastures
Deposited By: Ambus, Professor Per
ID Code:10144
Deposited On:14 Dec 2006
Last Modified:12 Apr 2010 07:34
Document Language:English
Status:Published
Refereed:Peer-reviewed and accepted

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